Isomerization of alkyl halides



April 19, 1949. J. A. cHENlcEK 2,437,965

ISOMERIZTION OF ALKYL HALIDES Filed Jan. so, 194e Patented Apr. 1 9", 1949 .lfoseph'A.V Riverside, .ass'ignonto a corporation'of Delaware, h y y Application January 30,-v i946; Seriana-*644,401 """iroiima (Cl.;196-7s 1;

This invention relates to zation of alkyl halides. .It is more4 particularly concerned AWith the treatment iof alkyl.- halides containing at least 'three carbon' atoms` with iluo'rine-containing yi'somerization catalysts at isomerizing conditions. It is also concerned with aprocess Vfor improving the quality of cracked gasolines.

' character of the hydrocarbon vand the" operating conditions such as contact time,'temperature, and the concentration of the reactants. VI iam principally interested inthe monol'1alogende7 rivatives of hydrocarbons. v y

When alkylhalides are formed by the addition of hydrogen halide to olen'mixtures or by the limited halogenation of paran mixtures, primary, secondary, and -tertiary valkyl halides are produced. However, because certain of the types vof alkyl halides are relatively more desirable f than the others, it has been found necessary to augment their supply.` This can be accomplished bythe use of my invention by is'oin'erizing those alkyl halides for which there'isA4 less demand to their more valuable counterparts.

In one embodimenti'nyinventionfconsis'ts of a process for the isomerization of 'alkyl halides which comprises subjectingan alkyl halide'con'- taining more than two carbon atoms vto the action of a ilumine-*containing isomerization catalyst under isomerizing "conditions,`

Attempts to improve the duality'ofcracked gasoline, particularlyv 'thermallyfcracked Agas;

line, by treatment with metal halide and mineral acid catalysts havel met with negligible success because of the extensive cracking and-y hydrogen transfer reactions which `occur.fBy,the use oi my invention, the antiknock ratingbi v'cracked gasoline can be improved Withoutthe simultane- L ous occurrence of extensive s idefre'actions' In a specific ernbodimentmy invention 'co sists line which comprises contacting *a fcracked'- gasolthe catalytic nomen! Universal Oil Products ;CQmpany, Chicago, Ill.,

lineA With VV*a :hydrogen 'halide 'under hydrohalo- 'genating conditions, 'separating amixture com- .I prisingfthe: alkyl halides thus produced and/un- 'Ifconverte'd "hydrocarbons from the` hydrogen ;:ha1'ide, subjecting said mixture to the actionv of iailuorine'econtaining isomerization catalyst underisomerizing conditions,v separating the isom- 4 =erate from ther isomerizationv catalyst, subjecting said isomerate to the action oi a dehydrohalo- ,genating catalyst under dehydrohalogenating .:.f;conditions,` separating hydrogen halide from Athe sfeiuentof therlast named step,and,recycling said Lhydrogen'halide to athe'hydrohalogenation step.

Thealkyl halidesfrused in my process -may be fluorides, chlorides, bromides,I and'iodidesbut, in'general', the fluorides are somewhat-less susceptible to isomerizationl than the other halides.

The halide should contain atleast three carbon atoms because methyl and ethyl halides, which contain 1 and 2 carbon atoms respectively, are not capable of undergoing isomerization. The

: alkyl halide may be primary, secondary, tertiary,

4on'dary butyl iiuoride, n-amyl or a mixture thereof. The limiting composition of the product in all'cases will be the equilibrium mixture. Examples of suitable compounds are n-propyl bromide, tertiary butyl chloride, seciodide, and

r 2--chloro-octane.

" Fluorine-containing isomerizationk catalysts maybe used-*which effect intramolecular reararangement in-alkyl halides containing more than three I vcarbon atoms.

The rearrangement `may consist of a change inthe carbon structure, a

migration of `the halogen atom, of both. kSuitable catalysts include anhydrous hydrogen fluoride; hydrogen fluoride+boron trifluoride; fluo- 1,;,fsulfo'nic acid; hydrogen fluoride-l-a metal salt su'chas potassium uoride; hydrogen uoride-l-a nonoxidizing acid, esten/or acid anhydride; bo-

lron triliuoride-l-uosulfonicacid; boron triluoride-l-an acid uoride such as potassium acid fluoride; hydrogen fluoride-l-hydrogen cyanide; hydrogen fluoride-i-a low boiling fluoride or oxyiiuoride selected from the group consisting of the fluorides I or' oxyluorides4 of sulfur, selenium,

"1vanadium,: silicon, and tungsten; hydrogen ilu- Voride-l-hydroxyiluoboric acid;

boron triuoride-l-nickel-i-hydrogen fluoride; and boron tri- ''uoride+nickel+water+hydrogen fluoride.`

VhThelLprocess'of my invention may be carried 'f-out"`sing either batch or. continuous operation.

"In-ia' simple batch -procedure .proportionate I' -'ani'oiints ofthe "alkyl: halide and Ythe 'iluorine-contalmngif'ismerizatinnii'catalystifmay' abe added to a reaction vessel and the contents heated and agitated for a time adequate to cause the desired degree of conversion. After a period of heating, the reaction Vessel may be cooled, the contents discharged, and a separation effected between the alkyl halides and the catalyst. This type of operation can readily be converted to a continuous basis by continuously charging regulated amounts of alkyl halide and catalyst to the reaction vessel, and simultaneously withdrawing regulated amounts of isomerate and catalyst from said vessel. A continuous separation can be made between the catalyst and the isomerate, and the former may then be recycled to the reaction vessel. Part of the used catalyst may be sent to regeneration means to remove the organic contarninants which tend to accumulate in said phase during the reaction.

The optimum conditions used for the isomeri- -ratus in which one of the objects of my invention may be accomplished. This object is the improvement of the anti-knock quality of a cracked gasoline. In order to simplify the explanation of the drawing, it is being considered in connection with the hydrochlorination of a full boiling range thermally cracked gasoline and the isomerization of the alkyl -chlorides in the presence ofanhydrous hydrogen fluoride with subsequent dehydrochlorination. It is not intended, however, that this simplication should unduly limit the generally broad scope of the invention.

Referring to the drawing, a cracked gasoline containing olerlns is introduced through line I containing Valve 2 into hydrochlorinator 3, wherein hydrogen chloride is reacted with the olefins in the gasoline to form alkyl chlorides. This reaction may be carried out in the liquid or vapor phase and in the presence or absence of contact agents. Among the agents which may be used to catalyze this reaction are adsorptive materials, such asl activated carbon, which have a microporous structure, and adsorptive metal oxide gels prepared by partially dehydrating hydrogel or gelatinous precipitates. This reaction is usually carried out at atmospheric temperature but temperatures as low as 80 C. and as high as 100 C. may be employed. The alkyl chlorides and the unconverted hydrocarbons are separated from the hydrogen chloride by means such as a settler or fractionator not shown in the drawing. The chlorides and hydrocarbons are passed through line 4 containing valve 5 into isomerizer 5, wherein the mixture is contacted with anhydrous hydrogen fluoride under isomerizing conditions. A substantial portion of the alkyl halides are converted to more highly branched isomers thereof. The ellluent from isomerizer 6 is passed through line 1 containing valve 8 into acid settler 9, wherein a fraction comprising chiey hydrogen fluoride is separated from the fraction comprising chiefly alkyl chloride and hydrocarbons. The catalyst layer is withdrawn through line I0 `containingvalve Il and the bulk of it is returned to isomerizer 6. A portion of it may be withdrawn through line I2 containing valve I3 and sent to a regeneration means wherein organic contaminants which accumulate in the catalyst phase during the reaction are removed. The alkyl halide-hydrocarbon fraction from settler 9 is Withdrawn through line I4 containing valve I5 and is passedinto hydrogen fluoride stripper I6. Hydrogenv uoride is removed therefrom as an overhead product through line II containing valve I8 and is returned to isomerizer 6. The bottoms from stripper I6 are withdrawn through line I9 containing valve 20 and are passed into dehydrochlorinator 2 I, which may be packed-withany of the known dehydrochlorinating catalysts, such as bauxite, barium chloride, various clays, etc. In this Vessel the alkyl chlorides are decomposed into olens and hydrogen chloride. The efuent from dehydrochlorinator 2i is passed through line 22 containing valve 23 into hydrogen chloride stripper 24. Hydrogen chloride is removed as an overhead product therefrom, and is returned to hydrochlorinator 3 through line 25 containing valve 26. Makeup hydrogen chloride may be added through line 29 containing Valve 30. The bottoms product from stripper 24 comprises olefin-containing cracked gasoline of higher octane number than that charged to the process, and is withdrawn through line 21 containing valve 28 and sent to storage.

Pumps, condensers, receivers, and the like, have been omitted from the drawing for the .sake of simplicity, but it is to be understood that they are to be used wherever needed.

The following example is given to illustrate the results that can be obtained by the use of this invention, but it is not intended to limit the generally broad scope of the invention.

Example I One-hundred and sixty-nine grams of secondary butyl chloride and 190 grams of anhydrous hydrogen fluoride were charged to a turbomixer and agitated for 30 minutes. The temperature was 75 F. at the beginning of the run and 100 F. at the end. The pressure was sufliciently high to maintain the alkyl chloride and the catalyst in the liquid phase. The contents of the bomb were demoved at the end of the run, a separation Ywas effected between the alkyl halides and the acid, and the former was then analyzed. The analysis showed that 8.2% of the secondary butyl chloride had been converted to tertiary butyl chloride. Inaddition, some high boiling material had been produced'in the reaction. Therefore, the ultimate or recycle yield of tertiary butylchloride is somewhat less than I claim as my invention:

1. A process for the production of tertiary alkyl halides which comprises subjecting a nontertiary alkyl halide containing more than 2 carbon atoms to the action of a catalyst predominating in substantially anhydrous hydrogen fluoride under isomerizing conditions.

2. The proce-ss of claim 1 further characterized in that the catalyst comprises boron fluoride in addition to the substantially anhydrous hydrogen fluoride.

3. A-process for the production of tertiary alvkyl halides which comprises subjecting a nontertiary alkyl halide containing more than 2 carbon atoms to the .action of a catalyst predominating in substantially anhydrous hydrogen fluoride, at an isomerization temperature and under a pressure sufcient yto maintain a Vsubstantial 5 portion of the reactants and the catalyst in the liquid phase.

4. The process of claim 3 further characterized in that the catalyst comprises boron fluoride in addition to the substantially anhydrous hydrogen fluoride.

5. A process for the production of tertiary alkyl chlorides which comprises subjecting a nontertiary alkyl chloride containing more than 2 carbon atoms to the action of a catalyst predominating in substantially anhydrous hydrogen iiuoride under isomerizing conditions.

6. The process of claim 5 further characterized in that the catalyst `comprises boron fluoride in addition to the substantially anhydrous hydrogen uoride.

7. A process for the treatment of cracked gasoline which comprises contacting a cracked g-asoline with hydrogen chloride under hydrochlorinating conditions to form alkyl chlorides in the gasoline, subjecting the gasoline containing alkyl chlorides to the action of an isomerization catalyst predominating in hydrogen fluoride under isomerizing conditions to isomerize at least a portion of said alkyl chlorides, separating the isomerate from the isomerization catalyst, subjecting said isomerate to the action of a dehydrochlorinating catalyst under dehydrochlorinating conditions, separating hydrogen chloride from the eiliuent of the last named step, and recycling said hydrogen chloride to the hydrochlorination step.

8. The process of claim 7 further characterized in that the isomerization catalyst com-prises substantially anhydrous hydrogen uoride and boron uoride.

9. A process for the production of a tertiary alkyl halide which comprises subjecting a secondary alkyl halide under isomerizing conditions to REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,102,655 Graul July 7, 1914 1,202,282 Graul Oct. 24, 1916 1,885,060 Hofman et al. Oct. 25, 1932 2,164,334 Marks July 4, 1939 2,374,819 Kanhofer et al May 1, 1945 2,412,726 Frey Dec. 17, 1946 FOREIGN PATENTS Number Country Date 535,435 Great Britain Apr. 9, 1941 OTHER REFERENCES Richters Organic Chemistry, translated by Spielmann, page 92 (P Blakistons Son, 1921).

Simons et al., Jour. Am. Chem. Soc, Vol. 60, pages 2267-2269 (1938).

Wiechert, Die Chemie, Vol. 56, pages 338-339 (1943). 

